Porosity, openness, and exposure: Identification of underlying factors associated with semi-outdoor spaces’ thermal performance and clustering in tropical high-density Singapore

•63 semi-outdoor spaces are characterised in terms of underlying factors (i.e. hypothetical constructs).•Exploratory Factor Analysis (EFA) analyses 11 spatial attributes of semi-outdoor spaces.•EFA reveals 3 underlying factors: volume porosity, perimeter openness & exposure to sky.•Such underlying factors are linked to the microclimate and predicted thermal comfort.•Such underlying factors are associated with how semi-outdoor environments are clustered.